It has been a problem to operate internal combustion engines, such as automotive engines using gasoline, and to, at the same time, protect the ecology from emissions such as nitrogen oxides, hydrocarbons and carbonmonoxides, as well as other noxious gasses. Furthermore, it has been difficult to accomplish the foregoing while maintaining good gas mileage, as well as good driveability. Many approaches to a solution of the foregoing problems have been directed toward operating a four cycle gasoline engine on a lean fuel mixture and it has been found that extremely lean fuel ratios approaching 20:1 afford substantial solutions to the foregoing problems. However, the usual four cycle internal combustion engine, using such a lean mixture, has not been capable of reasonable performance and has been difficult to start, as well as exhibiting other functional problems. It is believed that conventional four cycle internal combustion engines, such as automotive engines, do not operate properly on an air-fuel mixture ratio, such as in the range of 18:1 to 20:1 air-fuel ratio mixtures, due to the fact that most induction and combustion cycles are such that lean mixture, when in the presence of unscavenged products of combustion from the previous cycle, do not ignite readily and therefore spark plug ignition is not entirely reliable during the starting of such engines when attempting to operate them with a very lean fuel mixture.
Conventional four cycle internal combustion engines also operate with the upper surfaces of the pistons at substantially high temperatures due to the fact that they are not efficiently cooled by the fuel mixture entering the cylinder through the intake valve due to the fact that the piston moves away from the fuel mixture very rapidly as it enters at the head end of the cylinder and thus, upon compression of the fuel mixture toward the head end, the hot piston tends to cause relatively high ignition temperatures and relatively high combustion temperatures which aggrevate the nitrogen oxide emissions problem.
It is known that a lean burn air-fuel ratio tends to minimize hydrocarbon emissions and also carbon monoxide emissions and accordingly, a great many attempts have been made to operate conventional four cycle internal combustion engines on very lean fuel mixture ratios. But, such engines have not performed properly in this manner.